Method, system and apparatus for providing mobility management of a mobile station in WLAN and WWAN environments

ABSTRACT

A method, system and apparatus for internetworking WLAN and WWAN environments are disclosed. More specifically, a method, system and apparatus for providing mobility management of a mobile station in WLAN and WWAN environments are disclosed. Roaming and handoffs are discussed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to provisional application Ser.No. ______ (tbd), entitled “Method for Voice Internetworking BetweenLocal Area and Wide Area Mobile Wireless Networks,” filed on Jan. 2,2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to internetworking between wireless localarea networks (WLANs) and wide area mobile wireless networks.

[0004] 2. Discussion of Related Art

[0005] Subscribers are adopting wireless telephony in increasingly largenumbers. This trend is being fueled further by attractive rate plansthat are bringing the cost of telephony to acceptable levels for peoplein most walks of society. It is more common for people to rely almostexclusively on a mobile telephone for their telephony needs. In anoffice or enterprise environment, however, mobile telephony has notsurpassed wireline enterprise telephony for a number of reasons, salientamongst which are the following:

[0006] The weakness of R/F signals from the wide area networkinfrastructure within an office building, leading to problems inmobility management and voice quality.

[0007] The availability of special PBX features in office telephonysystems, such as abbreviated dialing, offer a strong incentive for thecontinued use of enterprise telephony solutions.

[0008] The situation at the present is that people employ two distincttelephony systems, one in the wireless wide area network, and another inthe enterprise premises that is a wireline telephony system, leading toa plurality of handsets, voice mailboxes and addressing mechanisms.

[0009] Parallel to these developments, wireless local area networks arebecoming increasingly popular for wireless data applications. In suchnetworks, reasonable bandwidth is available to enterprise-wide wirelessclients, e.g., in 802.11b WLAN networks up to 11 Mbps are available to awireless client. This bandwidth is more than sufficient to carry voiceas well. Moreover, widespread use of WLAN technology is driving down theprice of the technology.

[0010]FIG. 1 shows an exemplary wireless wide area network (WWAN) 100(also known as a wide area mobile wireless network). WWAN 100 includes aplurality of remote units (handsets) 102 in radio contact with one ormore antennae based systems called Base Transceiver System (BTS) 104that transceive the radio signals to/from the handsets. A plurality ofBTS communicate with a controller called the Base Station Controller(BSC) 106 via fixed links 108 using a variety of protocols andtechniques, such as TDM, IP etc. A plurality of BSC communicate with aswitch called the mobile switching center (MSC) 110 that providesconnectivity to a wide area switched telephone network (WSTN) 111. TheWSTN includes signaling links 113, such as SS7 links, and the publicswitched telephone network (PSTN) 112. As illustrated by MSC 115, an MSCmay include a control plane 117 for handling messages on the signalinglinks, which may be communicated according to a variety of protocols,such as IOS, GSM A interface, IS 41, GSM MAP, etc. The MSC 115 may alsoinclude a media gateway 119 that cooperates with the control plane forhandling the bearer circuits of the PSTN 112. Some modem MSCs, such asMSC 115, may also communicate on IP networks, such as IP network 120.

[0011] An MSC with its associated BSC and BTS collectively define acoverage area in which handsets are allowed to receive or transmittelephone calls. Incoming calls to a mobile handset arrive from the PSTNto a gateway MSC, e.g., 115, that then routes the call to the MSC 110,called a serving MSC, within whose coverage area the receiving handsetis currently roaming. Outgoing calls from a handset are routed to theserving MSC 109 of the originating handset from where the call is eitherrouted to the serving MSC of the receiving mobile handset via thegateway MSC or to the WSTN via the gateway MSC from where the WSTNroutes the call to a (wireline) handset.

[0012] In some arrangements, the gateway and serving MSC functions maybe implemented by the same physical entities. Subscribers are allowed toroam in the coverage area and while roaming the various entities of theWWAN cooperate to ensure that the wireless connectivity of the handsetis preserved under roaming. A handset may roam from the coverage area ofone set of BTS/BSC/MSC to the coverage area of another set ofBTS/BSC/MSC. The former set of BTS/BSC/MSC is called the source and thelatter set is called the target entities. A set of procedures has beendefined that mediate the handoff of the handset from the source to thetarget entities of the WWAN. As a consequence of the handoff procedures,an update of the location of the handset may occur. This is accomplishedby the handset sending a location update message to an MSC that routesthe message to a registry called the Home Location Register (HLR) 114using standard industry protocols such as IS-41, GSM-MAP, etc.

[0013] Various air interface technologies are used for the communicationbetween handsets 102 and BTS 104. These technologies include codedivision multiple access (CDMA), global system for mobile communications(GSM), Personal Digital cellular (PDC), etc., and various extensions andenhancements of these technologies such as CDMA2000, universal mobileterrestrial system (UMTS), international mobile telephone IMT-2000, etc.All such networks employ the above referenced entities in well known,albeit using different nomenclature, configurations to transceivetelephone calls. All this is well known to practitioners with ordinaryskill in the art.

[0014]FIG. 2 illustrates an exemplary wireless local area network (WLAN)200. WLAN includes one or more geographical areas (cells) called basicservice set (BSS) 202. A cell is controlled by a system called an accesspoint (AP) 204. Typically, a WLAN includes several BSS, each with itsassociated AP. The AP are interconnected usually with a wireline network206 typically using Ethernet in 802.x WLAN technologies. The APcommunicate with an enterprise router 208 that typically routes trafficwithin and out of an enterprise network. Wireless data clients 210 areallowed to roam within a defined BSS and across the defined BSS, withhandoff of the client from one AP to the adjoining AP in accordance toknown procedures. In typical WLAN implementations, the physical layeruses variety of technologies, e.g., in 802.11 WLAN implementations thephysical layer may use infrared, frequency hopping spread spectrum inthe 2.4 GHz Band, or direct sequence spread spectrum in the 2.4 GHzBand. The medium access layer (MAC) in addition to carrying out typicalfunctions performs additional functions such as packet fragmentation,re-transmission and acknowledgements.

[0015] The MAC layer supports two basic access mechanisms: thedistributed coordination function (DCF) and the point coordinationfunction (PCF). In DCF the basic access mechanism is a carrier sensemultiple access with collision avoidance (CSMA/CA) mechanism. A typicalexample is Ethernet that is a CSMA with collision detection (CD)mechanism. In CSMA protocols a client wishing to transmit senses themedium, and if the medium is found to be busy, i.e., is being used bysome other client, defers the transmission; otherwise it is allowed totransmit. There is always a possibility that two clients will sense themedium to be free and start transmissions thus resulting in collisions;therefore, collision avoidance and detection is very important in suchprotocols. For example, the 802.11 WLAN uses collision avoidance anddetection mechanisms. An 802.11 client wishing to transmit senses themedium and if found busy defers the transmission; otherwise, ittransmits. The receiver checks the receipt of a proper transmission (viathe cyclical redundancy check—CRC) and if found satisfactory, sends backan acknowledgement. Receipt of the acknowledgement will indicate to thetransmitter that the transmission was received properly. If noacknowledgement is received, the transmitter will retransmit until anacknowledgement is received or the transmitter decides to abort thetransmission. In order to further reduce the possibility of collisionscertain implementations also use the virtual carrier sense mechanism. Inthis scheme, a client wishing to transmit, first signals its intent bysending a request to send (RTS) to the intended receiver. The receiverresponds with a clear to send (CTS) that effectively “reserves” themedium for the transmitter and receiver. The transmitter may nowtransmit the intended information.

[0016] In those cases when a client wishing to transmit finds the mediumbusy, the client defers the transmission. The client is thus obliged tore-try to find the status of the medium. In standard approaches to thisproblem, an “exponential back off procedure” is used to determine thefrequency of re-trials. The method involves the choice of a randomnumber and awaiting that many time slots before a re-trial. If a re-tryfinds the medium busy again, the re-trial number is reducedexponentially. This back off procedure is also used after a successfultransmission and after each re-transmission.

[0017] When a client wishes to access a BSS (either after a power up orwhen first entering the BSS) it needs to get synchronization informationfrom the AP controlling the BSS. Two methods have been defined forclients to get this information. In the passive scanning method theclient waits to receive a “beacon frame” from the AP that is transmittedby the AP at regular intervals. The beacon frame contains thesynchronization information. In the second method, called activescanning, the client sends a probe to the AP and awaits a response tothe probe. Once the station finds an AP, it needs to be authenticated.This requires exchange of information between the AP and the client toestablish the authenticity of the client. Once the authenticationprocess is completed, the client starts the association process thatinvolves exchange of information between the client and the APs aboutthe location of the client and the capabilities of the BSS. At thecompletion of the association process, the client is ready for receivingor transmitting data.

[0018] In the PCF access mechanism, the AP gains control of the mediumupon sensing it to be free for a given length of time called the pointinter frame space (PIFS). The AP then assumes the role of thecoordinator and starts to poll all stations enumerated on a “poll list”maintained by the AP. When polled, a station is allowed to transmit. Theperiod in which the AP supports PCF mode is contention-free so mayprovide better opportunities for voice traffic. The AP must alternatethe DCF and PCF periods. All this is well known to practitioners withordinary skill in the art.

[0019] Therefore, what is needed is a method for internetworking of WLANand Wireless Wide Area Networks (WWAN) for voice communications withfull mobility management across the two networks and the preservation ofPBX features in the WWAN environment.

SUMMARY

[0020] The invention provides a method, system and apparatus forproviding mobility management of a mobile station in WLAN and WWANenvironments.

[0021] According to one aspect of the invention, a mobile switchingcenter (MSC) is provisioned to act as a serving MSC for a WLAN. A mobilestation detects the RF energy of the WLAN and validates its ability tobe a member of the WLAN. In response, the mobile station issues aregistration request to the serving MSC for the WLAN, and in response,the serving MSC for the WLAN causes a WWAN to recognize that the mobilestation is registered with the serving MSC for the WLAN and that themobile station is no longer served by a prior MSC. The mobile stationcommunicates to entities outside of the WLAN by communicating with theWLAN via a WLAN protocol and the WLAN communicates with the WWAN via theserving MSC for the WLAN.

[0022] Under another aspect of the invention, the mobile station issuesa registration request by sending a SIP Register message on the WLAN viaa WLAN air interface protocol to request registration therein, and theWLAN communicates the registration request to the MSC serving the WLAN.

[0023] Under another aspect of the invention, a mobile station detectsthe RF energy of the WLAN and validates its ability to be a member ofthe WLAN while the mobile station is participating in a call using aWWAN air interface protocol. In response thereto a message is sent to asource MSC that is servicing the call, indicating that a handoff isdesired. The source MSC analyzes the message, establishes itself as ananchor MSC, and establishes communication channels with a target MSCservicing the detected WLAN. The mobile station begins communicationwith the WLAN via a WLAN air interface. The WLAN forwards messages tothe target MSC serving the WLAN via IP communication, and the target MSCrelays those communication to the anchor MSC.

[0024] Under another aspect of the invention, a mobile stationdetermines that it should communicate via a WWAN air interface protocoland not via a WLAN air interface protocol. The mobile station issues aregistration request to the WWAN via a base station controller (BSC) andMSC corresponding to a location in which the mobile station resides. Thecorresponding MSC causes the WWAN to recognize that the mobile stationis registered with the corresponding MSC and that the mobile station isno longer served by a prior MSC which served the mobile station when itwas communicating according to a WLAN air interface protocol.

[0025] Under another aspect of the invention, a mobile stationdetermines that it should communicate according to a WWAN air interfaceprotocol while the mobile station is participating in a call under aWLAN air interface protocol. In response thereto, a message is sent to asource MSC that is servicing the call indicating that a handoff isdesired. The source MSC analyzes the message, establishes itself as ananchor MSC, and establishes communication channels with a target MSCservicing a geographic WWAN area in which the mobile station resides.The mobile station begins communication with the WWAN and the target MSCrelays those communication to the anchor MSC.

[0026] Under another aspect of the invention, the mobile station informsthe MSC serving the WLAN of the cell ids of the WWAN geographic area,and the source MSC uses the cell ids information to establishcommunication channels with the target MSC.

[0027] Under another aspect of the invention, a mobile stationdetermines that it should communicate according to a WWAN air interfaceprotocol while the mobile station is participating in a call under aWLAN air interface protocol. In response thereto a message is sent to asource MSC to request a temporary local directory number (TLDN). Thesource MSC provides a TLDN to the mobile station. The source MSC causesa called party of the call to be placed on hold and the mobile stationrequests a call to be made using the TLDN as a called party. The WWANcauses call connections to be made connecting the mobile station withthe TLDN to resume the call.

BRIEF DESCRIPTION OF THE DRAWING

[0028] In the Drawing,

[0029]FIG. 1 shows a prior art wireless wide area network (WWAN);

[0030]FIG. 2 shows a prior art wireless local area network (WLAN);

[0031]FIG. 3 shows an internetworked wireless network according tocertain embodiments of the invention;

[0032]FIG. 4 shows a multimode mobile station detecting the presence ofa WLAN according to certain embodiments of the invention;

[0033]FIG. 5 shows a multimode mobile station receiving cell idinformation from the macro network identifying relevant areas in whichthe mobile station may sense for a WLAN according to certain embodimentsof the invention;

[0034]FIG. 6 shows a multimode mobile station receiving cell idinformation from the macro network identifying public and otherenterprise WLANs according to certain embodiments of the invention;

[0035]FIG. 7 shows a multimode mobile station according to certainembodiments of the invention;

[0036]FIG. 8 shows an internetworked wireless network according tocertain embodiments of the invention in which a mobile station may roamfrom a WLAN environment and/or in which a handoff of servicing a mobilestation from a WLAN to a WWAN occurs;

[0037]FIG. 9 shows mobility management logic according to certainembodiments of the invention;

[0038] FIGS. 10-11 show specific mobility management logic according tocertain embodiments of the invention;

[0039]FIG. 12 shows mobility management logic according to certainembodiments of the invention;

[0040] FIGS. 13-4 show specific mobility management logic according tocertain embodiments of the invention;

[0041]FIG. 15 shows an internetworked wireless network according tocertain embodiments of the invention in which a mobile station may roamfrom a WWAN environment and/or in which a handoff of servicing a mobilestation from a WWAN to a WLAN occurs;

[0042]FIG. 16 shows mobility management logic according to certainembodiments of the invention;

[0043] FIGS. 17-8 show specific mobility management logic according tocertain embodiments of the invention;

[0044]FIG. 19 shows mobility management logic according to certainembodiments of the invention;

[0045] FIGS. 20-1 show specific mobility management logic according tocertain embodiments of the invention;

[0046]FIG. 22 shows logic for providing SMS to a mobile stationoperating in a WLAN environment according to certain embodiments of theinvention;

[0047]FIG. 23 shows logic for providing MWN service to a mobile stationoperating in a WLAN environment according to certain embodiments of theinvention;

[0048] FIGS. 24-5 show logic for handling intra enterprise callsaccording to certain embodiments of the invention;

[0049] FIGS. 26-7 show logic for handling an enterprise to PSTN callaccording to certain embodiments of the invention;

[0050]FIG. 28 shows logic for handling an enterprise to macro networkcall according to certain embodiments of the invention;

[0051]FIG. 29 shows an internetworked wireless network according tocertain embodiments of the invention;

[0052]FIG. 30 shows mobility management logic according to certainembodiments of the invention; and

[0053]FIG. 31 shows an internetworked wireless network according tocertain embodiments of the invention in which PBX services areintegrated.

DETAILED DESCRIPTION

[0054] Preferred embodiments of the invention provide voiceinternetworking between WLANs and WWANs and effectively unify these twodisparate technologies. Consequently, users no longer need to suffer theproblems associated with multiple handsets, addresses, and voicemailboxes. As will be explained below, under certain embodiments agateway MSC (GMSC) switch of the WWAN with some associated modificationsto the WLAN client provides the logic necessary for unification. Inessence the GMSC simultaneously acts as a serving MSC for WLAN voicetraffic.

[0055]FIG. 3 illustrates an exemplary embodiment of the presentinvention. The WWAN components are like those described above inconjunction with FIG. 1 except that MSC 302 includes some newinternetworking logic discussed below to handle the unification of theWLAN and WWAN to make it act as one macro network 300. Among otherthings, the MSC 302 acts as a serving MSC for the WLAN. The WLAN andWWAN are now effectively connected by the IP links 304. Voice trafficalong with the associated signaling and control messages to and from theWLAN are carried on the set of IP links 304 from the enterprise to theIP interfaces of the MSC 302. The WLAN components are also like thosedescribed above, except that the handsets or wireless data clients 310now include multimode devices capable of operating in the WLAN or WWANenvironments, as will be explained below.

[0056] The MSC 302 allows telephone calls to be completed betweenclients of the WWAN 100 and WLAN 200. The WLAN clients are free to roamin the WLAN environment and may also roam in the WWAN environmentwithout any manual interventions required of the subscriber. The voicetraffic from the WLAN to the MSC 302 may utilize any of the known voicecoding technologies. For CDMA networks the Enhanced Variable Rate Codec(EVRC) may be used and for GSM networks Adaptive Multi-rate (AMR) codingcould be used. The coded voice is then carried as RTP/UDP/IP packets onthe IP links 304. The control and signaling information is also carriedon the IP links 304 from the WLAN 200 to the MSC 302. In certainembodiments the control and signaling information is carried in theformat of Session Initiation Protocol (SIP) messages with additionalinformation elements (IEs) described as a part of the present inventionfor control of hand offs of the handsets.

[0057] Voice internetworking in certain embodiments is facilitated bythe use of a multimode handset 310 that may operate in a WLAN or WWANenvironment. The WLAN and WWAN (multimode) phone 310 at any time shouldbe able to automatically determine if it is capable of using WLAN accessinstead of a macro network carrier (GSM, CDMA, UMTS, TDMA, PDC, etc.).

[0058] The presence of a WLAN can be inferred by detecting RF energy inthe permitted 802.11b/a spectrum (2.4 GHz band for 802.11b/802.11g and 5GHz band for 802.11a). As shown in FIG. 4, the mobile station 310 mayinitiate a detection 402 of RF energy in the relevant spectrum. Aftersuccessful energy detection, the mobile station can detect if a validWLAN 200 is present by one of the two methods:

[0059] Passive Scanning: the station 310 searches for a beacon framebroadcast by the 802.11x AP 204

[0060] Active Scanning: the station 310 transmits probe request framesand waits for probe response frames from the AP 204.

[0061] As part of the beacon frame or the probe response, the AP sends aSSID (1-32 octets length string) that identifies the AP 204. The mobilestation 310 compares this SSID with a list of SSIDs (which may includeranges) and if there is a match, infers that the WLAN 200 is a validnetwork for it to gain access. The mobile station 310 goes through anauthentication process after a successful SSID match. If theauthentication succeeds, the mobile station proceeds with theassociation process whereby the mobile station joins the WLAN network asa valid and legal client (node).

[0062] The mobile station 310 is a priori provisioned with the validlist of SSIDs and SSID ranges. The SSID comparison avoids the mobilestation from entering into authentication or association processes infunctioning WLAN networks on which it could never be authenticated. Forexample, let the mobile station MS1 belong to Enterprise E1 that uses SSID En1SSID1. When the mobile station enters the Enterprise El, thebeacon search succeeds and further an SSID match occurs and hence themobile station proceeds with the authentication process. On successfulauthentication, it proceeds with the association process and gainsaccess to the WLAN service. When the same mobile station MS 1 entersanother enterprise that also happens to have a valid 802.11 WLAN butwith a different SSID (say, En2SSID2) the SSID does not match the SSIDin the mobile and hence the mobile station does not even attempt toinitiate authentication (and hence presumes that the WLAN service is notavailable). The provisioning of SSIDs in the mobile station can beinitiated from the macro network 300 using over the air provisioningprocedures (OTASP/OTAPA) in the case of CDMA networks and equivalent inGSM/UMTS networks (using Short Message Service). In order to preventeavesdropping of the SSIDs in the macro network, the message itselfcould be encrypted using the same key used in the mobile station formacro network authentication/encryption (A-key or SSD).

[0063] The periodic detection and subsequent discovery of the presenceof the WLAN impacts the battery life of the mobile station. It isdesirable to minimize the battery consumption and one way to achievethis in the multimode phone is to minimize the number of detection ordiscovery attempts and at the same time preserving the ability to jumpon to the enterprise WLAN if it is available. Two observations on theuse of the multimode mobile stations 310 enable the reduction in thenumber of detection/discovery attempts:

[0064] The number of areas where the enterprise Wireless LAN service isavailable for the subscriber is limited; for example, enterprisesubscribers may be limited to get access to their WLAN services in theirenterprise locations only.

[0065] The multimode mobile station is always attempting to stayconnected to the macro network (CDMA, GSM, UMTS, etc.). For example, aCDMA phone on detection of a valid IS-95/IS-2000 signal will attemptregistration with the IS-41 core network; a GSM/UMTS phone on detectionof a valid GSM/UMTS signal will attempt registration with the GSM-MAPcore network. As a consequence of registration, the cell id that isknown to both the macro network and the mobile station, indicates thecurrent location of the mobile station.

[0066] By relating the above two facts, the macro network 300 candetermine when the mobile station 310 should be attempting to detect ordiscover the enterprise WLAN. As shown in FIG. 5 in a preferredembodiment of the present invention, the macro network 300 can send 502information regarding the detection or discovery process to the mobilestation 310 on a successful network registration. The informationincludes the macro network cell-ids where the mobile station 310 shouldattempt to detect or discover 402′ an enterprise WLAN. The cell-id is agross measure and hence can cover a very large area (in the order of fewsquare miles in rural/suburban areas) or a very small area (in the orderof few hundred square meters in dense urban areas).

[0067] As an exemplary manifestation of the method of the presentinvention, consider a CDMA (IS-95) subscriber who is also an enterprisesubscriber to 802.11 services in Building W located in Tewksbury, Mass.When the subscriber enters the CDMA switching area in Tewksbury, hisIS-95 phone initiates a network registration. As part of thisregistration, the macro network 300 determines that the subscriber maypossibly enter the coverage area of the WLAN service in Building W; thatis, the macro network correlates the information that the subscriber andBuilding W are in the Tewksbury switching area. The macro network nowprovides 502 the cellid information where the W building is located tothe subscriber's mobile station 310 and a trigger that WLAN sensingshould now begin. On receipt of this information, the mobile stationstarts to scan for the 802.11 beacon, specifically looking for a matchwith the SSID list of the APs in Building W. This detection will notsucceed until the subscriber enters the BSS 202. Upon successfuldetection of the beacon from the AP 204, the mobile station 310 of thesubscriber de-registers from the macro network 300 and registers withthe serving MSC 302 for the WLAN 200. When the mobile station 310 roamsin the WLAN 200, it continues to sense the RF energy strength of theWWAN 100 and WLAN 200. If it detects that the WLAN RF strength decreasesbelow some threshold value and the WWAN strength is above a thresholdvalue, it initiates a registration process with the macro (WWAN) network100.

[0068] As mentioned before, the cell ids of the macro network 300 maydesignate very large geographical areas. If the cell id relates to asmall geographical area then the chances of minimizing power consumptionin the mobile station are better since the detection or discoveryprocess is limited to the smaller geographical area. Under someembodiments the availability of GPS (Geographical Positioning Satellite)information integrated into the mobile stations may be used. Since GPSinformation is more accurate as compared to cell id information, the useof GPS information will further reduce the geographical area in whichthe detection or discovery process needs to be initiated, thus leadingto more savings in the power consumption of the mobile station.

[0069] The list of cell-ids provided by the macro network to the mobilestation can consist not only of enterprise locations that the subscribercan roam into but potentially other “enterprises” or “public areas” aswell. For example, the macro network service provider may have a roamingarrangement with a public enterprise LAN such as a restaurant or ahotel. Referring to FIG. 6, when a subscriber 310 registers with themacro network, it would be beneficial to also receive 602 the cell-idswhere the subscriber's enterprise is located but also the cell-ids wherethe public LANs are located in the same switching area.

[0070] The delivery of the location information or more directinstruction to start (or stop) searching for WLAN beacon in the mobilestation 310 can be accomplished using standard Short Message Service(SMS), or by using logic based in a Service Control Point (SCP), or bymodifying the the HLR or using a Proxy HLR entity. (See, e.g., U.S.patent application 09/845,703, filed Apr. 30, 2001 for an example of aproxy HLR, which application is hereby incorporated by reference in itsentirety.) When the mobile station 310 registers with the MSC/HLR, themacro network can deliver the cell-id list, beacon search/stopinstruction etc., as a SMS (short message service) with a specific type.The SMS message is sent after a successful response to the LocationUpdate initiated by the mobile station 310. The MSC 302 can have switchbased logic that initiates a trigger on location update that causes aswitch resident or Service Control Point (SCP) resident application togenerate the SMS message with the cell-ids. For example, a switch couldbe programmed to trigger an SCP on receipt of a location update. TheSCP-resident logic may then send the location and sensing instructionsto the mobile station. Alternatively, the HLR 114 can be modified toperform the same task on successful processing of an IS-41 REGNOTrequest or GSM-MAP UPDATE LOCATION request. In other embodiments, aProxy HLR may be employed. The Proxy HLR intercepts all messagesintended for the HLR from the MSC. Registration messages received fromthe multimode WWAN and WLAN clients are handled by the Proxy HLR whereasmessages from all the other clients are forwarded to the HLR without anymodifications.

[0071]FIG. 7 shows a handset 310 according to exemplary embodiments ofthe present invention. For example, the handsets include logic tocommunicate according to a WLAN air interface protocol (such as 802.xx)and to communicate according to a WWAN air interface protocol. Asdescribed herein, the mobile station may select to use one of the airinterface logic unit based on its sensing of relevant radio spectrum.Moreover, a handset may support more than one WWAN macro networktechnology. For CDMA handsets it is assumed that a WLAN modem will beadded to the handset. Additionally, the capability to transport voice asSIP/RTPIUDP/IP packets will be needed. The network sensing methoddiscussed in the previous section along with the modifications requiredto reduce the detection and discovery traffic by utilizing cell-ids, inthe preferred embodiment of the present invention, are to be captured byspecial computer programs running on the computing platform of thehandset.

[0072]FIG. 8 shows the movement of a mobile station 310 from a WLANenvironment 200 to a WWAN environment 100. Under certain embodiments ofthe invention, the mobile station 310 registers in the WWAN environment100 as it roams from the WLAN 200 into the WWAN. Likewise theappropriate handoff must be made as well. The mobile station 310, usingthe network sensing method described above, infers that it needs toregister with the WWAN environment.

[0073] Mobile Station (MS) leaves WLAN and enters WWAN: Referring toFIGS. 8 and 9, the registration and handoff are implemented in certainembodiments as follows. The logic starts at 900 and proceeds to 902 inwhich the mobile station 310 issues a registration request to the (new)serving base station controller (BSC) 106 in the WWAN. The BSC 106transmits 904 a Location Update message to its serving MSC 110. Theserving MSC 110 in the WWAN requests 906 a registration from the HLR114. The HLR 114 sends 908 a de-registration request to the (previous)serving MSC 302 in WLAN. Optionally, the (previous) serving MSC 302 maysend 910 a SIP registration cancel request to the mobile station 310that will respond with a confirmation. This may facilitate “clean up” or“tear down” at the mobile station, since it is no longer communicatingvia the WLAN. The (previous) serving MSC 302 responds 912 to thede-registration message to the HLR 114. The HLR confirms 914 theregistration request to the (new) serving MSC 110 in the WWAN. The (new)serving MSC 110 accepts 916 the Location Update from the BSC 106. TheBSC 106 acknowledges 918 the registration from the mobile station 310.

[0074] In an exemplary embodiment of the present invention, if the WWANis an IS-41 network then the registration, de-registration andconfirmatory messages will use IS-41 protocol elements. The variousspecific messages used, as explained with reference to FIG. 9, are shownin FIG. 10. In another exemplary embodiment, if the WWAN is a GSM-MAPnetwork then the registration, de-registration and confirmatory messageswill use GSM-MAP protocol elements. The various specific messages usedas explained with reference to FIG. 9 are shown in FIG. 11.

[0075] Hard Handoff from WLAN to WWAN: In this case, the mobile station310, while engaged in a telephone call, roams from WLAN 200 to WWAN 100.The WLAN environment needs to handoff 802 the mobile station 310 fromthe WLAN serving MSC 302 to WWAN serving MSC 110. Since the mobilestation 310 is engaged in a call within WLAN, the SIP client is managingthe call in the mobile station 310. This client needs to inform the WLANserving MSC 302 the cell ids of the WWAN macro network. In the preferredembodiment of the present invention, the SIP command “SIP INFO” isoverloaded with this cell id information. The overloaded informationelements are so indicated in the logic described below in connectionwith FIG. 12.

[0076] The logic starts at 1200 and proceeds to 1202 in which the mobilestation 310 informs the WLAN serving MSC (Source MSC) 302 that a handoffis required. This may be based on the network sensing method. Asdiscussed above, in the network sensing method, the mobile station 310senses both the WLAN and the WWAN networks and chooses one of them basedon the relative RF strengths. During the sensing procedure, the cell idof the WWAN network becomes known to the mobile station 310. The mobilestation 310 uses the cell id to initiate a hard handoff to the WWANnetwork from the WLAN network. In the handoff required message the cellid of the WWAN network is sent to the WLAN switch. This is an overloadedSIP command. The cell id is used so that the MSC that was serving theWLAN and is now the anchor knows which other MSC to connect to. Thesource MSC 302 issues 1204 a facility directive (FD) to the WWAN MSC(Target MSC) 110 that allows it open a bearer channel on PSTN 112 (forexample) from Source MSC 302 to Target MSC 110. This allows the sourceMSC to serve as an anchor for the communication, having a new “leg” tothe target MSC and an existing pathway to the other entity(ies) on theexisting call. The Target MSC 110 sends 1206 a handoff request to the(Target) BSC 106. The Target BSC 106 commences 1208 RF channel signalingwith the mobile station 310. The Target BSC 106 sends 1210 handoffrequest acknowledgement to Target MSC 110. The Target MSC 110 responds1212 to the facility directive request back to the Source MSC. TheSource MSC 302 sends 1214 a message to the mobile station 310 indicatingthat a handoff may be commenced. For example, this message may be sentas an overloaded SIP message. This message effectively informs themobile station that it may select and start using the appropriate RF andmodulation circuitry to communicate with the WWAN. The mobile station310 sends 1216 a message to the source MSC 302 to commence handoff.Again, this message may be sent as an overloaded SIP message. The mobilestation 310 commences 1218 RF channel signaling with Target BSC 106. Themobile station 310 sends 1220 handoff completion message to Target BSC106. Again, this message may be sent as an overloaded SIP message. TheTarget BSC 106 acknowledges 1222 handoff order to the mobile station310. The Target BSC 106 sends 1224 handoff complete message to TargetMSC 110. The Target MSC 110 sends 1226 message to Source MSC 302indicating that the mobile station 310 is on channel with Target BSC106. The Source MSC 302 sends 1228 a message to the mobile station 310indicating that it may clear any resources assigned this transaction.The mobile station 310 responds 1230 with OK acknowledgement.

[0077] In an exemplary embodiment of the present invention, if the WWANis an IS-41 network then the messages, excluding the overloadedmessages, will use IS-41 protocol elements. The various specificmessages used as explained with reference to FIG. 12 are shown in FIG.13. In another exemplary embodiment, if the WWAN network is a GSM-MAPnetwork, the protocol elements used will be GSM-MAP. The variousspecific messages used as explained with reference to FIG. 12 are shownin FIG. 14.

[0078]FIG. 15 shows the case of the mobile station 310 roaming from aWWAN 100 to WLAN 200 environment. The mobile station 310, using thenetwork sensing method described above, senses the RF strength in theproximity of the WLAN and decides to start using the WLAN environment,thus initiating a registration request. As outlined above, the mobilestation may use the cell id information to determine when to startsensing the WLAN.

[0079] Mobile Station (MS) enters WLAN from WWAN: As the mobile station310 enters a WLAN 200 from a WWAN 100, the logic of FIG. 16 is followed.The logic starts in 1600 and proceeds to 1602 in which the mobilestation 310 issues 1602 a registration request to the WLAN Serving MSC302 upon sensing the WLAN RF energy strength, as described above. Thisis done via a SIP message (e.g., a broadcast message), which the WLANServing MSC receives. The WLAN Serving MSC 302 sends 1604 a registrationrequest to the HLR 114. The HLR issues 1606 a de-registration request tothe (previously) Serving WWAN MSC 110. Upon confirmation ofde-registration, the HLR sends 1608 a registration response confirmationto the WLAN MSC 302. The WLAN MSC 302 confirms 1610 the registration tothe mobile station 310.

[0080] In an exemplary embodiment of the present invention, a mobilestation 310 roams from IS-41 WWAN to 802.11 WLAN. The various specificmessages used as explained with reference to FIG. 16 are shown in FIG.17. In a preferred embodiment of the present invention, the mobilestation 310 issues a “SIP Register” message to the WLAN Serving MSC 302that sends a IS-41 Registration Notification (REGNOT) to the HLR 114.The HLR sends a Registration Cancellation request to the WWAN MSC 110that was serving the mobile station 310 (to de-register the mobilestation) and upon receiving a confirmation of the de-registration, sendsa confirmation of registration to the WLAN Serving MSC 302 which thensends a “SIP 200 OK” (confirmation) message back to the mobile station310, completing the transaction. In another exemplary embodiment of thepresent invention, if the mobile station 310 enters 802.11 WLAN fromGSM-MAP WWAN, the registration, de-registration and confirmationmessages from the HLR will employ the corresponding GSM-MAP protocolelements. The various specific messages used as explained with referenceto FIG. 16 are shown in FIG. 18.

[0081] Hard Handoff from WWAN to WLAN: In this case the mobile station310, while engaged in a telephone call, roams from WWAN 100 to WLAN 200.The unified WLAN and WWAN environment needs to handoff 1502 the mobilestation 310 from the WWAN Serving MSC 110 to WLAN Serving MSC 302.Certain embodiments of the invention implement such a handoff using thelogic of FIG. 19.

[0082] The logic begins at 1900 and proceeds to 1902 in which the BSC106 serving the mobile station 310 (Serving BSC) decides 1902, basedupon information received from the mobile station 310 that may be usingthe Network Sensing Method described above, that a handoff is required.It sends a handoff required message to the Source MSC 110. The SourceMSC 110 issues 1904 a facility directive to the WLAN MSC (Target MSC)302 that allows it to open a bearer channel on PSTN 112 from Source MSC100 to Target MSC 302. The mobile station 310 sends 1906 a handoffrequest to the Target MSC 302; under certain embodiments of the presentinvention, this message is sent using SIP with overloaded commands. TheTarget MSC 302 acknowledges 1908 the request. The mobile station 310acknowledges 1910 the response of the Target MSC 302. The Target MSC 302responds 1912 to facility directive request to Source MSC 110. TheSource MSC 110 sends 1914 a message to Source BSC 106 that a handoff maybe commenced. The Source BSC 106 sends 1916 a handoff directive tomobile station 310. The mobile station 310 sends 1918 a message toacknowledge. The Source BSC 106 sends 1920 a message to Source MSC 110that handoff has commenced. The mobile station 310 sends 1922 handoffcompletion message to Target MSC, again via an overloaded SIP message.The target MSC acknowledges 1924 handoff order to mobile station 310.The Target MSC 302 sends 1926 message to Source MSC 110 indicating thatthe mobile station 310 is on channel with target MSC. The Source MSC 110sends 1928 a message to Source BSC 106 to clear facilities. The SourceBSC 106 responds 1930 with OK clear complete.

[0083] In an exemplary embodiment of the present invention, if the WWANis an IS-41 network then the messages, excluding the overloadedmessages, will use IS-41 protocol elements. The various specificmessages used as explained with reference to FIG. 19 are shown in FIG.20. In another exemplary embodiment, if the WWAN network is a GSM-MAPnetwork, the protocol elements used will be GSM-MAP. The variousspecific messages used as explained with reference to FIG. 19 are shownin FIG. 21.

[0084] Delivery of Short Message Service (SMS) in WLAN: SMS is a servicethat is typically supported in the WWAN 100 by a network entity known asthe Short Messaging Service Center (SMSC). A mobile station 310 whileroaming in a WLAN 200 preferably supports SMS service. Under certainembodiments the logic of FIG. 22 implements the SMS service in WLAN 200.

[0085] The SMS Messaging Center sends 2202 a SMS request (Short MessageDelivery Point to Point—SMDPP) to the WLAN Serving MSC 302. In certainembodiments of the present invention the Serving MSC 302 overloads andsends 2204 the SIP INVITE message with SMS payload to the mobile station310. The mobile station 310 responds 2206 with an OK acknowledgement.Serving MSC 302 indicates 2208 to the MS that the transaction iscomplete. The mobile station 310 responds 2210 OK. The Serving MSC 302responds 2212 with SMDPP Request Response to the SMS Message Center.

[0086] Delivery of IS-41 Message Wait Notification (MWN) in WLAN: MWN isa feature of WWAN 100. A mobile station 310 while roaming in WLAN 200preferably supports MWN service. Under certain embodiments the logic ofFIG. 23 provides MWN in WLAN.

[0087] The IS-41 HLR 114 sends 2302 a Qualification DirectoryNotification (with MWN Type) to the WLAN Serving MSC 302. In certainembodiments of the present invention the Serving MSC 302 overloads 2304the SIP INVITE message with MWN info to the mobile station 310. Themobile station 310 responds 2306 with an OK acknowledgement. The ServingMSC 302 indicates 2308 to the mobile station 310 that the transaction iscomplete. The mobile station 310 responds 23100K. The Serving MSC 302responds 2312 with Qualification Directive Notification Response Requestto the IS-41 HLR.

[0088] Intra Enterprise Telephone Call: In this case a mobile station310 (MS1) while roaming in the WLAN 200 initiates an intra enterprisecall to another mobile station (MS2). Under certain embodiments, allinteractions with MS 1 and MS2 are carried out in SIP. The logic toimplement such calls is described in connection with FIG. 24.

[0089] MS1 initiates 2402 a call request to the WLAN Serving MSC 302.The MSC 302 receives the request and asks 2404 the HLR 114 to locateMS2. HLR 114 responds 2406 with location of MS2. The MSC 302 issues 2408an invitation to MS2. MS2 acknowledges 2410 request. The MSC 302acknowledges 2412 the acknowledgement of MS2. The MSC 302 sends 2414acknowledgement to MS1 indicating that the call may now proceed. MS1acks 2416, and the call between MS1 and MS2 proceeds.

[0090] In an exemplary embodiment of the present invention, the intraenterprise call proceeds using EVRC (Extended Variable Rate Coding) onRTPIUDP/IP packets. The requests to locate MS2 in IS-41 networks may useIS-41 protocol elements. FIG. 25 shows another exemplary embodiment inwhich the call proceeds by using GSM EFR (Extended Full Rate Coding) onRTP/UDP/IP packets with HLR inquiries using GSM-MAP protocol elements.

[0091] Enterprise to PSTN Telephone Call: In this case a mobile station310 initiates a telephone call to a PSTN handset. The logic of certainembodiments of the invention to support such a call is described inconnection with FIG. 26.

[0092] The mobile station 310 using SIP sends 2602 a call request to theServing WLAN MSC 302. The Serving MSC 302 asks 2604 the HLR 114 tolocate the called party. The HLR 114 responds 2606 with the location(PSTN switch) of the called party. The Serving MSC 302 requests 2608 aconnection capable of carrying voice traffic from the Media Gateway ofthe MSC 302. The Media Gateway responds 2610 with a connection response.The Serving MSC 302 sends 2612 a connection request to the PSTN switchassociated with the called telephone number (i.e., the switch to whichthe called party is connected). The PSTN Switch acknowledges 2614receipt of request. The Serving MSC 302 tells 2616 the mobile station310 that it is trying the called party. The PSTN Switch responds 2618with connection information. The Serving MSC 302 sends 2620 a message tomobile station 310 indicating it is OK to proceed with call. The mobilestation 310 acknowledges 2622 and conversation may now begin.

[0093] In an exemplary embodiment of the present invention the voicetraffic may be carried as EVRC on RTP/UDP/IP packets between the mobilestation 310 and the Serving MSC 302 and as 64K PCM voice between theServing MSC 302 and the PSTN switch. The HLR interactions may be carriedout using IS-41 protocol elements. FIG. 27 shows another exemplaryembodiment in which the HLR interactions may be carried out usingGSM-MAP protocol elements and the voice between the mobile station 310and the Serving MSC 302 may be carried as GSM EFR on RTP/UDP/IP packets,and as 64K PCM voice circuits between the Serving MSC and the PSTNswitch.

[0094] Enterprise to WWAN GSM telephone Call with Tandem Free Operation(TFO): In this case a mobile station 310 (MS1) initiates a telephonecall to another mobile station (MS2) roaming in a GSM network. Sinceonly mobile stations are involved in this call, it is possible to carrythis call in a tandem-free operation; i.e., carry the call as GSM EFRwithout having to uncompress/decompress to 64K PCM. The logic of certainembodiments to implement such a call is described in connection withFIG. 28.

[0095] The mobile station 310 using SIP sends 2802 a call request to theServing WLAN MSC 302. The Serving MSC 302 asks 2804 the HLR 114 tolocate the called party using GSM MAP. The HLR 114 asks 2806 the ServingGSM MSC 110 to locate MS2, i.e., provide roaming number associated withMS2. The GSM MSC 2808 responds with MS2's roaming number to HLR 114. TheHLR 114 sends 2810 routing response to WLAN Serving MSC 302. The ServingMSC 302 requests 2812 a connection capable of carrying voice trafficfrom the Media Gateway with TFO on trunk side. The Media Gatewayresponds 2814 with a connection response. The Serving MSC 302 sends 2816a connection request to the GSM MSC. The GSM MSC 110 acknowledges 2818receipt of request. The Serving WLAN MSC 302 tells 2820 the mobilestation 310 that it is trying the called party. The GSM MSC 110 responds2822 with connection information. The Serving MSC 302 sends 2824 amessage to mobile station 310 indicating it is OK to proceed with call.The mobile station 310 acknowledges and conversation may now begin.

[0096] In this exemplary embodiment of the present invention the voicetraffic may be carried as GSM EFR on RTP/UDP/IP packets between the MSand the Serving MSC and as GSM EFR in 64K DSO as a TFO channel betweenthe WLAN Serving MSC (Media Gateway) and the GSM MSC (or the GSM RadioAccess Network).

[0097] Other Variations

[0098] A basic mechanism of the present invention is the handoff of themobile station as it roams during a call from a WLAN to the WWANenvironment. This mechanism assumes the existence of trunks connectingthe WLAN and WWAN switches using a standard mobility management protocolsuch as IS-41. FIG. 29 shows an exemplary embodiment of a method thatmay be used to affect handoffs in the absence of such connectivity, andexemplary logic is discussed in connection with FIG. 30. As shown in thefigure and in accordance to the present invention as describedpreviously, the mobile station 310 (MS) while engaged in a telephonecall with Party A, who may be using a PSTN handset 2902 or a WWAN mobilehandset 2904, senses both the WLAN and WWAN environments and determinesthat the WLAN environment is waning in intensity whereas the WWANenvironment is gaining in intensity. Under such an arrangement, mobilestation 310 may determine 3002 that handoff is imminent. Upon makingthis determination mobile station 310 requests 3004 the WLAN switch 302to issue it a Temporary Local Directory Number (TLDN). As is well knownto practitioners in the art a TLDN may be used by other telephoneexchanges to route a call to the switch issuing the TLDN. Havingreceived the TLDN the mobile station 310 continues roaming and themobile station 310 or the WLAN switch or both may find 3006 that theconnectivity between the mobile station 310 and the WLAN switch has beenlost. In such an eventuality the WLAN switch temporarily places 3008party A on hold (WLAN may inform Party A about the on going state ofaffairs by playing a pre-recorded announcement). The mobile station 310upon sensing the WWAN environment and upon successful completion ofregistration in the WWAN environment, requests a call to be placed usingthe TLDN as the destination (called party). The WWAN switch routes 3010the call to the WLAN switch using its routing logic dependent on theTLDN. The WLAN switch recognizes 3012 the TLDN and connects Party A tothe incoming call. Thus, Party A and the MS resume the on going callalbeit with an interruption.

[0099] Many enterprises make use of a Private Branch Exchange (PBX). PBXsystems typically provide a feature-rich environment to the attachedtelephones, such as abbreviated dialing, multiparty calls and the like.In certain embodiments of the present invention a WLAN switch may beused in conjunction with a PBX system.

[0100]FIG. 31 shows an exemplary embodiment of this arrangement. TheWLAN 200 is connected to the PBX 3102 via standard supported interfacessuch as ISDN PRI. Telephone calls originating from a handset connectedto the PBX and destined for a WLAN-controlled handset may be deliveredto the WLAN switch 3104 via the standard interface. The WLAN switch mayuse the standard interface to deliver telephone calls to the PBX.

[0101] A mobile station 310 may make calls using the WLAN air interface,and such calls will be communicated over the wired LAN 206 to WLANswitch 2904 via the IP links of LAN 206. Switch 3104 will thencommunicate the call signaling (and eventually voice or other data) overISDN PRI link 3106 to the PBX switch 3102 which will handle the call asif it were from a PBX phone 3108 and thus provide the PBX services tothe mobile station. For example, if the mobile station used anabbreviated dialing scheme, the PBX would make the appropriateconnections and communication would be conducted via the PBX switch3102.

[0102] For internal calls, the WLAN switch 3104 essentially acts as aprotocol converter, receiving the mobile station signaling and data asIP and providing it to the PBX via the ISDN PRI links as ISDNinformation.

[0103] For external calls, certain embodiments operate as follows. TheWLAN switch 3104 detects that the mobile station desires to call anoutside party. This may be done by analyzing the called partyinformation, for example, to see if certain numbering plan informationis used, such as prefixing the called number with the number ‘9’. Insuch case, the switch 3104 communicates with the WWAN switch 3112 andrequests a TLDN to be later associated with the called party informatione.g., called party number “123.” When it receives such TLDN, the switch3104 then makes a request to the PBX switch 3102 via link 3106 toconnect the circuits associated with the mobile station to the WWANswitch 3112 using the TLDN i.e., requests the PBX to connect a call tothe TLDN as the called party. The WWAN switch 3112 recognizes that theincoming call request with TLDN is for the previously remembered calledparty number 123 (i.e., WWAN switch 3104 associates the issued TLDN withpreviously received called party number “123” from WLAN switch 3104) andproceeds to route call to called party number “123” as dictated bystandard routing logic. Thus, PBX 3102 requests call to destination TLDNbut WWAN switch 3112 recognizes that the call is actually meant fordestination “123” and routes the call to “123”. The TLDN serves as a tagidentifying the “signaling” on IP link 3114 and the request from the PBXon ISDN PRI link 3110. In this fashion, any subsequent signaling or link3114 associated with mobile station 310 will be associated with thecorrect bearer circuits on link 3110.

[0104] In terms of mobility management, roaming may proceed as explainedabove. Hard handoffs may proceed as explained above if there existmobility management trunks between the WWAN switch 3312 and the WLANswitch 3104. This logic is shown in FIGS. 12-14 and 1921 with theassociated descriptions of hard handoffs under various networkconditions. In the absence of such trunks a handoff may proceed withregard to the use of TLDN as a handoff mechanism—namely as the mobilestation roams into a WWAN area and loses radio contact with the WLAN,the mobile station will perform a handoff by automatically reconnectingwith the call by using the TLDN. In this instance, the WLAN switch mayinform the mobile station of the TLDN to use either during call set up,or as explained above in response to the mobile station's request (e.g.,the WLAN switch 3104 may cache the TLDN and await the request of themobile station).

[0105] In this arrangement the WWAN MSC 3112 anchors the call. Certainvariations are possible. For example, during handoffs the WWAN MSC maytear down the links previously used to the PBX. This is efficient fortwo party calls. However to support calls in which multiple parties inthe PBX domain participate, the links to the PBX must remain up. In thissituation, the WWAN MSC 3112 must patch in the mobile station to theexisting call.

[0106] The above discussion and the following claims at times refer tospecific WLAN standards such as 802.11. This is typically done to use avery specific example. In many instances reference is made to 802.x. Thedesignation of ‘x’ is used to indicate a wider applicability, i.e., toany of the 802 WLAN standards.

[0107] Though some of the discussion is with reference to voice calls,persons skilled in the art that the above teachings and following claimsare also directed to data calls as well. It will be further appreciatedthat the scope of the present invention is not limited to theabove-described embodiments, but rather is defined by the appendedclaims, and that these claims will encompass modifications of andimprovements to what has been described.

What is claimed is:
 1. A method of managing mobility of a mobile stationacross an 802.xx wireless local area network (WLAN) and a wireless widearea network (WWAN) in which a mobile switching center (MSC) has beenprovisioned to act as a serving MSC for the WLAN, comprising: (a) themobile station detecting the RF energy of the WLAN and validating itsability to be a member of the WLAN; (b) in response to step (a), themobile station issuing a registration request to the serving MSC for theWLAN; (c) in response to step (b), the serving MSC for the WLAN causingthe WWAN to recognize that the mobile station is registered with theserving MSC for the WLAN and that the mobile station is no longer servedby a prior MSC; (d) the mobile station communicating to entities outsideof the WLAN by communicating with the WLAN via a WLAN protocol and theWLAN communicating with the WWAN via the serving MSC for the WLAN. 2.The method of claim 1 wherein the mobile station issues a registrationrequest by sending a SIP Register message on the WLAN via a WLAN airinterface protocol to request registration therein, and the WLANcommunicates the registration request to the MSC serving the WLAN. 3.The method of claim 1 further including the MSC serving the WLAN sendinga de-registration request to an MSC that previously served the mobilestation.
 4. The method of claim 1 wherein the MSC serving the WLAN sendsa registration notification message to an HLR to update the WWAN withlocation information of the mobile station, and wherein the HLRcommunicates with a prior MSC to cancel service thereat of the mobilestation,
 5. The method of claim 1 wherein the MSC serving the WLAN sendsan update location message to an HLR to update the WWAN with locationinformation of the mobile station, and wherein the HLR communicates witha prior MSC to cancel service thereat of the mobile station, and whereinthe HLR communicates with the MSC serving the WLAN to insert thereat themobile station as a subscriber for service.
 6. The method of claim 1wherein a mobile station detects the RF energy of the WLAN and validatesits ability to be a member of the WLAN while the mobile station isparticipating in a call using a WWAN air interface protocol and inresponse thereto sending a message to a source MSC that is servicing thecall that a handoff is desired; the source MSC analyzing the message,establishing itself as an anchor MSC, and establishing communicationchannels with a target MSC servicing the detected WLAN; the mobilestation beginning communication with the WLAN via a WLAN air interface;the WLAN forwarding messages to the target MSC serving the WLAN via IPcommunication; and the target MSC relaying those communication to theanchor MSC.
 7. The method of claim 6 wherein the mobile stations sendsvia a WLAN air interface protocol a handoff request message as anoverloaded SIP command and the WLAN communicates the handoff requestmessage to the target MSC.
 8. The method of claim 1 further including amobile station determining that it should communicate via a WWAN airinterface protocol and not via a WLAN air interface protocol; the mobilestation issuing a registration request to the WWAN via a base stationcontroller (BSC) and MSC corresponding to a location in which the mobilestation resides; the corresponding MSC causing the WWAN to recognizethat the mobile station is registered with the corresponding MSC andthat the mobile station is no longer served by a prior MSC which servedthe mobile station when it was communicating according to a WLAN airinterface protocol.
 9. The method of claim 8 wherein a mobile stationdetermines that it should communicate according to a WWAN air interfaceprotocol while the mobile station is participating in a call under aWLAN air interface protocol and in response thereto sending a message toa source MSC that is servicing the call that a handoff is desired; thesource MSC analyzing the message, establishing itself as an anchor MSC,and establishing communication channels with a target MSC servicing ageographic WWAN area in which the mobile station resides; the mobilestation beginning communication with the WWAN and the target MSCrelaying those communication to the anchor MSC.
 10. The method of claim9 wherein the mobile station informs the MSC serving the WLAN of thecell ids of the WWAN geographic area, and wherein the source MSC usesthe cell ids information to establish communication channels with thetarget MSC.
 11. The method of claim 10 wherein the mobile station usesan overloaded SIP Info message to communicate the cell id information tothe source MSC.
 12. The method of claim 8 wherein a mobile stationdetermines that it should communicate according to a WWAN air interfaceprotocol while the mobile station is participating in a call under aWLAN air interface protocol and in response thereto sending a message toa source MSC to request a temporary local directory number (TLDN) thesource MSC providing a TLDN to the mobile station; the source MSCcausing a called party of the call to be placed on hold and the mobilestation requests a call to be made using the TLDN as a called party; theWWAN causing call connections to be made connecting the mobile stationwith the TLDN to resume the call.
 13. A wireless communication system,including a wireless local area network (WLAN) including logic tocommunicate according to a WLAN air interface protocol; a wireless widearea network (WWAN) including logic to communicate according to a WWANair interface protocol, the WWAN including at least one MSC for servingthe WLAN and in IP communication therewith; a mobile station includinglogic to communicate according to the WLAN air interface protocol, logicto communicate according to the WWAN air interface protocol, and logicto communicate mobility management messages to the WLAN as overloadedSIP messages for forwarding to the at least one MSC.